Investment Securities - Summary of Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available for sale, Amortized Cost
Amortized Cost	$ 231,419	$ 231,514
Available for sale, Fair Value
Total	226,504	231,507
Carrying value of investment securities pledged	117,400
Total debt securities
Available for sale, Amortized Cost
Within one year	524
After one year, but within five	46,954
After five years, but within ten	23,841
After ten years	150,865
Amortized Cost	222,184	215,574
Available for sale, Fair Value
Within one year	528
After one year, but within five	46,525
After five years, but within ten	22,947
After ten years	147,218
Total	$ 217,218	$ 214,941